Shimano Di2 hydraulic disc brakes revealed

Leaked photo shows Shimano have developed Di2 hydraulic disc brakes for the road

Michiel van der Heijden's disc CX bike

So long as the big players were absent from the hydraulic road disc debate, you could pretty much come down on either side. But if Shimano and SRAM both think it's going to work, then it's probably time to sit up and take note.

Michiel van der Heijden rides cyclocross for the Shimano-sponsored Rabobank team and he helpfully posted a snap of his bike on Twitter yesterday before heading off for a ride. Not just any old bike, though: a previously unseen disc-only Carbon Giant CX frame running Di2… and hydraulic discs.

There's no official word from the component manufacturer on this kit so we're stuck with what we've got in the pic, but with no master cylinder visible anywhere on the bike it's obviously in the lever hood. We'd expect that, anyway: with Di2 there's precious little else in there so there should be plenty of room.

Spy shots of the SRAM system made it look like they were struggling to fit the cylinder in; Shimano's lever is more or less the same shape as a mechanical one. The drivetrain is Dura-Ace but the levers appear to be Aluminium; whether that's just because they're prototypes is anyone's guess.

The callipers themselves look a fair bit like Shimano's M785 XT units; they're the same shape and you can see the cooling fins of the Ice-Tech pads poking out of the top. Heat build up has often been touted as the main issue for discs on the road so it would make sense to use that technology which allows the brakes to run significantly cooler.

The rotors are both 140mm, probably XTR-level RT98s. This is a CX bike, so it won't necessarily be going near any long alpine descents; we'll wait and see what rotor sizes Shimano go for on the roadgoing versions of this system which will surely follow. They're bolted on to Shimano-branded wheels with what looks like a carbon rim and a 2-cross lacing, but they could be pretty much anything.

Giant have a close working relationship with Shimano; last time we went out to a press launch with them (for Ultegra Di2) the kit was bolted on to pre-production samples of the new TCR Advanced frame. In fact, it was the first time we got to ride it. So it wouldn't surprise us if they were working in tandem with Shimano on this in order to work towards a launch sometime later in the year. All, as they say, will be revealed...

David has worked on the road.cc tech team since July 2012. Previously he was editor of Bikemagic.com and before that staff writer at RCUK. He's a seasoned cyclist of all disciplines, from road to mountain biking, touring to cyclo-cross, he only wishes he had time to ride them all. He's mildly competitive, though he'll never admit it, and is a frequent road racer but is too lazy to do really well. He currently resides in the Cotswolds.

30 comments

Excellent. This means there'll soon be lots of lightweight frames, forks, wheels, STIs and brakes available on eBay at knock-down prices when all the suckers who simply must have the latest thing, no matter how marginal or non-existent the gain, sell off their rim-brake-versions of everything.

I will be one of these people, but you know what, marginal gains, I never heard so much shit in my life, anybody who has ridden a mountain bike knows full well that the brakes are amazing compared to the crap on road bikes, and you know what, road bikes go faster and actually need better brakes.

So mock all you want, but for me, anything which means I can stop faster... when say some twat in a car pulls out in front of me gets my vote and money every day over lets say saving 20 grams on a new carbon seat post.

Well said mikeprytherch. Spot-on analysis as far as i am concerned. I put off having disc brakes on my mountain bike on the argument that i had enough power to lock the wheel with V brakes, why would i want more. However, once i bit the bullet...wow, more control, better wet weather performance, no rim wear. Bring on road discs i say!

Actually, this now makes a lot more sense - i never really got the point of electronic shift systems before (a solution in search of a problem) but combining the two makes a lot of sense. That said, I still think discs make most sense because of the options they give you in relation to rims (material, lack of wear etc.) And braking in the wet - as someone else already pointed out, I can already lock my wheels up no probs in the dry.

That said, I still think discs make most sense because of the options they give you in relation to rims (material, lack of wear etc.) And braking in the wet - as someone else already pointed out, I can already lock my wheels up no probs in the dry.

This. I don't need more power generally on the road, or better modulation. The stopping power and modulation of hydraulics is more important to me on a mountain bike, where I've got a much bigger tyre contact patch and more grip. But the real advantages come from (a) wet weather performance - particularly in comparison with long reach calipers on my winter bike, which are still never as good as their short reach counterparts, and (2) the ability to play around with rim materials and designs without the need for a braking surface or the worry that you are literally scrubbing away your high end rims.

From an aesthetics point of view, I'm still not sure about them - but for pure performance, it's got to be a leap forward...

I will be one of these people, but you know what, marginal gains, I never heard so much shit in my life, anybody who has ridden a mountain bike knows full well that the brakes are amazing compared to the crap on road bikes, and you know what, road bikes go faster and actually need better brakes.

So mock all you want, but for me, anything which means I can stop faster... when say some twat in a car pulls out in front of me gets my vote and money every day over lets say saving 20 grams on a new carbon seat post.

I will be one of these people, but you know what, marginal gains, I never heard so much shit in my life, anybody who has ridden a mountain bike knows full well that the brakes are amazing compared to the crap on road bikes, and you know what, road bikes go faster and actually need better brakes.

So mock all you want, but for me, anything which means I can stop faster... when say some twat in a car pulls out in front of me gets my vote and money every day over lets say saving 20 grams on a new carbon seat post.

agreed !

Looool. We go faster Mike because we don't use the brakes so much But money is an issue and can not be readily discounted. We both know when you buy a bike that is only the start of the costs. Just look at the cost of Shim D12 and campy eps. As an add on it is a bitch of a cost. Maybe if they can roll it out in the factory at marginal costs then a great idea, but retrospective fitting...how do you structurally attach it to a frame. Change is not such a bad thing but you can't also ignore physics. If you lock up your brakes whether caliper or disc...the tyres will break free (Newtons laws). In my humble opinion a good idea but also a marketing ploy to sell more bikes. And I can't see disc brakes being cheap and in the road bike world where weight is 'sacremont', a hard sell.

I've got a flat-bar with hydro discs and a carbon road bike with very expensive, very stiff long drop rim brakes - and there is simply no comparison. Finger-tip modulation with the hydros and grab and hope with the rim-brakes. As soon as I can (and before the next winter in any case) I'll be getting a disc-equipped road bike. Why don't you try some hydro discs before you knock them?

Looool. We go faster Mike because we don't use the brakes so much But money is an issue and can not be readily discounted. We both know when you buy a bike that is only the start of the costs. Just look at the cost of Shim D12 and campy eps. As an add on it is a bitch of a cost. Maybe if they can roll it out in the factory at marginal costs then a great idea, but retrospective fitting...how do you structurally attach it to a frame. Change is not such a bad thing but you can't also ignore physics. If you lock up your brakes whether caliper or disc...the tyres will break free (Newtons laws). In my humble opinion a good idea but also a marketing ploy to sell more bikes. And I can't see disc brakes being cheap and in the road bike world where weight is 'sacremont', a hard sell.

we're not going to be retrofitting discs, they'll gradually become more popular on new bikes. OEM costs won't be so much of a hike.

the whole 'locking your wheel up' thing is a red herring. i can lock my wheel up by jamming my pump in the spokes. that doesn't make it as good a stopping solution as a disc brake.

disc brakes mean better modulation, less force at the lever for the same amount of braking power meaning easier braking and less fatigue, better performance in adverse conditions, less overall maintenance, no rim wear, even braking on out-of-true wheels and no aluminium paste all over your fingers when you change a flat.

the pros won't want them much, and can't have them anyway cause they're not approved. but for normal people they make an awful lot of sense for most types of riding.

hydraulics will be the top-end choice but i expect to see more and better mechanical units too. Hayes CX-5 and Avid BB-7 are good already, looking forward to the new Tektro Spyre...

I just bought a new carbon bike and I am putting my hands over my ears......all I am hearing is money, money and more money....loool. . However, I will check them out first to see what all the fuss is about. As I carress my beautiful carbon bike called Aphrodite, I whisper,'No baby! Me love you long time'

That's exactly the problem, locking up your wheel... Just cause you can lock it up easily doesn't mean they're good brakes. Good brakes offer consistency, modulation, and power. Disc brakes offer that far better than rim calipers.

The thing everyone is forgetting is that your fitting disc brakes to a wheel with no traction. The contact surface of the tyre is so small that it'll skid, I'd rather the pads slip than the tyre, imagine touching the brakes in a wet corner and the front wheel locking up #gravelrash!